Compressors may be used in a wide variety of industrial and residential applications to circulate refrigerant within a refrigeration, heat pump, HVAC, or chiller system (generically “refrigeration systems”) to provide a desired heating or cooling effect. In any of the foregoing applications, the compressor should provide consistent and efficient operation to ensure that the particular application (i.e., refrigeration, heat pump, HVAC, or chiller system) functions properly.
Residential air conditioning and refrigeration systems may include a protection device that intermittently trips the system, which will cause discomfort to a homeowner, eventually resulting in a visit to the home by a serviceperson to repair a failure in the system. The protection device may shut down the compressor when a particular fault or failure is detected to protect the compressor from damage. In addition, protection devices may also detect a pressure within the compressor or between the compressor and associated system components (i.e., evaporator, condenser, etc.) in order to shut down the compressor to prevent damage to both the compressor and system components if pressure limits are exceeded.
The types of faults that may cause protection concerns include electrical, mechanical, and system faults. Electrical faults have a direct effect on the electrical motor in the compressor while mechanical faults generally include faulty bearings or broken parts. Mechanical faults often raise the internal temperature of the respective components to high levels, thereby causing malfunction of, and possible damage to, the compressor.
System faults may be attributed to system conditions such as an adverse level of fluid disposed within the system or to a blocked flow condition external to the compressor. Such system conditions may raise an internal compressor temperature or pressure to high levels, thereby damaging the compressor and causing system inefficiencies or failures. To prevent system and compressor damage or failure, the compressor may be shut down by the protection system when any of the aforementioned conditions are present.
Conventional protection systems typically sense temperature and/or pressure parameters as discrete switches and interrupt power supply to the motor should a predetermined temperature or pressure threshold be experienced. Parameters that are typically monitored in a compressor include the temperature of the motor winding, the temperature of the spiral wraps or scrolls (for a scroll-type compressor), the pressure at discharge, the electrical current going to the motor, and a continuous motor overload condition. In addition, system parameters such as a fan failure, loss of charge, or a blocked orifice may also be monitored to prevent damage to the compressor and system. A plurality of sensors are typically required to measure and monitor the various system and compressor operating parameters. Typically, each parameter measured constitutes an individual sensor, thereby creating a complex protection system in which many sensors are employed.
The most common protection arrangements for residential refrigeration systems employ high/low pressure cutout switches and a plurality of sensors to detect individual operating parameters of the compressor and system. The sensors produce and send a signal indicative of compressor and/or system operating parameters to processing circuitry so that the processing circuitry may determine when to shut down the compressor to prevent damage. When the compressor or system experiences an unfavorable condition, the processing circuitry directs the cutout switches to shut down the compressor.
Sensors associated with conventional systems are required to quickly and accurately detect particular faults experienced by the compressor and/or system. Without a plurality of sensors, conventional systems would merely shut down the compressor when a predetermined threshold load or current is experienced, thereby requiring the homeowner or serviceperson to perform many tests to properly diagnose the cause of the fault prior to fixing the problem. In this manner, conventional protection devices fail to precisely indicate the particular fault and therefore cannot be used as a diagnostic tool.